Added whenTableHasColumn and whenTableNotHasColumn to Schema Facade

Author: eusonlito

src/Illuminate/Support/Facades/Schema.php

@@ -15,6 +15,8 @@
  * @method static bool hasColumn(string $table, string $column)
  * @method static bool hasColumns(string $table, array $columns)
  * @method static bool dropColumns(string $table, array $columns)
+ * @method static void whenTableHasColumn(string $table, string $column, \Closure $callback)
+ * @method static void whenTableNotHasColumn(string $table, string $column, \Closure $callback)
  * @method static bool hasTable(string $table)
  * @method static void defaultStringLength(int $length)
  * @method static array getColumnListing(string $table)